1. Field of the Invention
The present invention relates to a turn signal switch device that is additionally provided in a steering column or the like of an automobile and is used as a signal indicator, and particularly, to a canceling mechanism that automatically returns an operating lever included in the turn signal switch device to a neutral position.
2. Description of the Related Art
A turn signal switch device of an automobile rotatably supports a proximal end of an operating lever in a housing integrated with a steering column or the like, and rotationally operates a distal end of the operating lever from a neutral position to either right or left direction-indicating position, and thereby a lamp for left turn or right turn flickers. In such a turn signal switch device, in order to hold the operating lever in three positions including the right and left direction-indicating positions and the neutral position, a cam surface is provided in an inner surface on the side of the housing, and a driving body that engages the cam surface is provided on one side of the operating lever via a spring. Further, a canceling mechanism for automatically returning the operating lever to the neutral position when a steeling wheel is rotationally operated in a direction opposite to an indicating direction in a state where the operating lever has been rotationally operated to either right or left direction-indicating position is additionally provided (for example, refer to U.S. Pat. No. 5,949,040□ corresponding to JP-A-269901).
FIG. 7 is a transverse sectional view showing the schematic configuration of a conventional turn signal switch device including this type of canceling mechanism, FIG. 8 is a plan view of the canceling mechanism, and FIG. 9 is an explanatory view of the operation of the canceling mechanism shown in FIG. 8.
In these drawings, reference numeral 100 represents a housing, and the housing 100 is fixed to a column cover, a combination switch, etc. (not shown) that are stator members of a steering system. A guide shaft 101 and a pivot 102 is erected from an inner bottom face of the housing 100 at a predetermined distance from each other, a first tong hole 103a of a first lever member 103 is fitted to the guide shaft 101, and a second lever member 104 is rotatably journalled to the pivot 102. The first lever member 103 has a second tong hole 103b, and the second tong hole 103b is fitted to a connecting pin 104a erected from the second lever member 104. Further, an abutting portion 103c and a cam portion 103d are erected from both front and rear ends of the first lever member 103, and the cam portion 103d has a cross-section that is formed in a semicircular shape. One arm portion 105a of the torsion coil spring (torsion coiled spring) 105 is hooked to the first lever member 103, and the first lever member 103 is resiliently biased in the longitudinal direction of both the tong holes 103a and 103b by the torsion coil spring 105. A winding portion 105b of the torsion coil spring 105 is inserted onto a boss 106 erected from the inner bottom face of the housing 100, and the other arm portion 105c is latched on a side watt of the housing 100. Further, the second lever member 104 has a first opening 104b and a second opening 104c, and both the openings 104b and 104c are in positions that face each other across the pivot 102.
An operating lever 107 is supported by the housing 100 so as to be rotatable about a pair of pivots 108, and a V-shaped cam surface 109 that has a pair of locking portions 109a on both sides thereof is formed inside the housing 100. A holder 110 is attached to the operating lever 107, and the operating lever 107 and the holder 110 integrally rotate in a horizontal direction with a straight fine connecting both the pivots 108 as an axis of rotation. A driving body 111 is slidably held at a distal end of the holder 110, and a tip of the driving body 111 is always brought into pressure contact with the cam surface 109 by a spring whose illustration is omitted. Further, a cam portion 112 and a receiving portion 113 are suspended from a member (not shown) that is integrally provided in the holder 110, the cam portion 112 faces the cam portion 103d of the first lever member 103, and the receiving portion 113 reaches the inside of the second opening 104c of the second lever member 104.
In the turn signal switch device configured in this way, in a cases where the operating lever 107 is in the neutral position, as shown in FIG. 7, the tip of the driving body 111 abuts on a central valley portion of the cam surface 109, and the driving body 111 is stably held in the position by the resilience of the spring that is not shown. At this time, as shown in FIG. 8, the cam portion 112 on the side of the operating lever 107 and the cam portion 103d of the first lever member 103 abut on each other at their apexes, and the first lever member 103 retreats against the biasing force of the torsion coil spring 105. Accordingly, the abutting portion 103c of the first lever member 103 is located out of a rotational locus of a canceling projection 114 that rotates in conjunction with the steeling wheel, and even if the steeling wheel is rotated in this state, the canceling projection 114 does not abut on the abutting portion 103c of the first lever member 103, and the operating lever 107 is maintained in the neutral position.
When the operating lever 107 is rotated in the direction of either an arrow A or an arrow B of FIG. 7 from the neutral position, the tip of the driving body 111 is locked to the locking portions 109a beyond the slope of the cam surface 109, and is stably held in the position by the locking portions 109a. For example, when the operating lever 107 is rotated in the direction of the arrow B of FIG. 7, the cam portion 112 and the receiving portion 113 are displaced to positions shown in (a-1) of FIG. 9 from FIG. 8 in conjunction with the rotation. Therefore, the cam portion 112 on the side of the operating lever 107 deviates from the apex of the cam portion 103d of the first lever member 103. As a result, the first lever member 103 receives the resilient force from the arm portion 105a of the torsion coil spring 105, and advances in the longitudinal direction of both the tong holes 103a and 103b, and the abutting portion 103c of the first lever member 103 abuts on an outer peripheral face of the canceling projection 114. Further, with the rotation of the operating lever 107 in the direction of the arrow B, switching operation of a contact point whose illustration is omitted is performed, and a lamp for right turn flickers.
When the steeling wheel is rotationally operated in a right-turn direction from the right-turn rotation state of the operating lever 107 shown in (a-1) of FIG. 9, the canceling projection 114 rotates in the direction of the arrow B white it comes into sliding contact with the abutting portion 103c of the first lever member 103, and when the canceling projection 114 has rotated by a predetermined angle θ1 as shown in (a-2) of FIG. 9, the abutting portion 103c of the first lever member 103 deviates from the outer peripheral face of the canceling projection 114, and advances into the rotational locus. Thereafter, when the steeling wheel is rotationally operated in the opposite direction (the direction of the arrow A) as shown in (a-3) of FIG. 9, the canceling projection 114 bumps against the abutting portion 103c of the first lever member 103 during the returning operation thereof. As a result, since the first lever member 103 rotates in the clockwise direction about the guide shaft 101, and the torque thereof is transmitted to the second lever member 104 via the connecting pin 104a from the second tong hole 103b, thereby rotating the second lever member 104 in the clockwise direction about the pivot 102, the second opening 104c of the second lever member 104 is rotationally displaced upward in this drawing. Since this causes a peripheral edge of the second opening 104c to press the receiving portion 113 upward, the driving body 111 deviates from the locking portions 109a of the cam surface 109, and shifts to the central valley portion, and the operating lever 107, and the first and second lever members 103 and 104 automatically return to the neutral position shown in FIG. 8.
On the other hand, when the operating lever 107 is rotated in the direction of the arrow A of FIG. 7 from the neutral position, the cam portion 112 and the receiving portion 113 are displaced to positions shown in (b-1) of FIG. 9 from FIG. 8 in conjunction with the rotation. Therefore, the cam portion 112 on the side of the operating lever 107 deviates from the apex of the cam portion 103d of the first lever member 103. As a result, the first lever member 103 receives the resilient force from the arm portion 105a of the torsion coil spring 105, and advances in the longitudinal direction of both the tong holes 103a and 103b, and the abutting portion 103c of the first lever member 103 abuts on an outer peripheral face of the canceling projection 114. Further, with the rotation of the operating lever 107 in the direction of the arrow A, switching operation of a contact point whose illustration is omitted is performed, and a lamp for left turn flickers.
Then, when the steeling wheel is rotationally operated in a left-turn direction from the left-turn rotation state of the operating lever 107 shown in (b-1) of FIG. 9, the canceling projection 114 rotates in the direction of the arrow A white it comes into sliding contact with the abutting portion 103c of the first lever member 103, and when the canceling projection 114 has rotated by a predetermined angle θ2 as shown in (b-2) of FIG. 9, the abutting portion 103c of the first lever member 103 deviates from the outer peripheral face of the canceling projection 114, and advances into the rotational locus. Thereafter, when the steeling wheel is rotationally operated in the opposite direction (the direction of the arrow B) as shown in (b-3) of FIG. 9, the canceling projection 114 bumps against the abutting portion 103c of the first lever member 103 during the returning operation thereof. As a result, the first lever member 103 rotates in the counterclockwise direction about the guide shaft 101, and the torque thereof is transmitted to the second lever member 104 via the connecting pin 104a from the second tong hole 103b, thereby rotating the second lever member 104 in the counterclockwise direction about the pivot 102. Therefore, the second opening 104c of the second lever member 104 is rotationally displaced downward in this drawing. Since this causes the peripheral edge of the second opening 104c to press the receiving portion 113 downward, the driving body 111 deviates from the locking portions 109a of the cam surface 109, and shifts to the central valley portion, and the operating lever 107, and the first and second lever members 103 and 104 automatically return to the neutral position shown in FIG. 8.
However, the aforementioned conventional turn signal switch device has a drawback in that, when the steeling wheel is rotationally operated in the same direction as the rotational direction of the operating lever 107 from a state where the operating lever 107 has been rotationally operated to a right turn or left-turn position, the angle (release angle) θ1 or θ2 when the first lever member 103 deviates from the outer peripheral face of the canceling projection 114 and advances into the rotational locus, may vary depending on to the rotational direction of the steeling wheel. This is because the contact place between the first lever member 103 and the arm portion 105a of the torsion coil spring 105 varies depending on the rotational direction of the first lever member 103, and accordingly, a difference is caused in the resilient force of the torsion coil spring 105 that presses the first lever member 103 in its advancing direction.
That is, when the steeling wheel is rotationally operated in the same direction as the rotational direction of the operating lever 107 from the right-turn rotation state of the operating lever 107, the canceling projection 114 is displaced to the position shown in (a-2) of FIG. 9 from (a-1) of FIG. 9, and the first lever member 103 deviates from the outer peripheral face of the canceling projection 114 and advances into the rotational locus. In this process, when the first lever member 103 rotates so that the abutting portion 103c may approach the winding portion 105b of the torsion coil spring 105, a contact place between a spring receiving portion of the first lever member 103 and the arm portion 105a of the torsion coil spring 105 moves toward the winding portion 105b, the torsion coil spring 105 deforms so that its deflection may be increased. Therefore, the torsion coil spring 105 biases the first lever member 103 in the advancing direction along the longitudinal direction of both the tong holes 103a and 103b with a comparatively large resilient force.
In contrast, when the steeling wheel is rotationally operated in the same direction as the rotational direction of the operating lever 107 from the left-turn rotation state of the operating lever 107, the canceling projection 114 is displaced to the position shown in (b-2) of FIG. 9 from (b-1) of FIG. 9, and the first lever member 103 deviates from the outer peripheral face of the canceling projection 114 and advances into the rotational locus. In this process, when the first lever member 103 rotates in a direction in which the abutting portion 103c is separated from the winding portion 105b of the torsion coil spring 105, a contact place between the spring receiving portion of the first lever member 103 and the arm portion 105a of the torsion coil spring 105 moves toward the distal end of the arm portion 105a, the torsion coil spring 105 deforms so that its deflection may be decreased. Therefore, the torsion coil spring 105 biases the first lever member 103 in the advancing direction along the longitudinal direction of both the tong holes 103a and 103b with a comparatively small resilient force.
As a result, when the canceling projection 114 rotates in the direction of the arrow B, the force that the torsion coil spring 105 pushes out the first lever member 103 in the advancing direction becomes large. Thus, when the first lever member 103 deviates from the outer peripheral face of the canceling projection 114 and advances into the rotational locus, the abutting portion 103c easily deviates from the outer peripheral face of the canceling projection 114. However, when the canceling projection 114 rotates in the direction of the arrow A, the force that the torsion coil spring 105 pushes out the first lever member 103 in the advancing direction becomes small. Thus, even at an angle to be released, the first lever member 103 hardly deviates from the outer peripheral face of the canceling projection 114 and consequently, the tip of the first lever member 103 is dragged and rotated by the canceling projection 114. Therefore, as shown in (a-2) of FIG. 9 and (b-2) of FIG. 9, the release angle θ2 (about 35 degrees) of the first lever member 103 when the canceling projection 114 rotates in the direction of the arrow A may become larger compared with the release angle θ1 (about 26 degrees) of the first lever member 103 when the canceling projection 114 rotates in the direction of the arrow B.